JPH08120306A - Production of iron-base sintered alloy valve seat excellent in wear resistance - Google Patents

Abstract

PURPOSE: To produce Fe base sintered alloy valve seat excellent in wear resistance by dispersing/distributing Co base alloy hard particle in the matrix of Fe base alloy while interposing the alloy layer of Ni principal component. CONSTITUTION: In the valve seat made of Fe base sintered alloy having the composition in which Co base alloy hard particle is dispersed/distributed in the matrix of Fe base alloy, on the boundary part between the hard particle and matrix, the alloy layer having Ni principal component is continuously or intermittently made present. The valve seat is obtained in such a manner that each component of Fe base alloy constituting the matrix and Ni base alloy coated Co alloy particle are mixed in the prescribed blending ratio and compacted/sintered. Thus, the adhesion of hard particle to matrix is improved, and the valve seat excellent in wear resistance is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an Fe-based sintered alloy valve seat having excellent wear resistance.

[0002]

2. Description of the Related Art Conventionally, it is well known that many valve seats made of an Fe-based sintered alloy having a structure in which hard particles are dispersed and distributed in a matrix have been proposed and put to practical use.

[0003]

On the other hand, in recent years, the performance and output of various internal combustion engines have been remarkably high and the operation speed has been remarkably high. Although the situation is becoming more severe, in the case of the above-mentioned conventional Fe-based sintered alloy valve seat,
Under the more severe conditions, the hard particles are liable to be peeled from the base material, and the service life is reached in a relatively short time.

[0004]

Therefore, the present inventors have
From the above-mentioned viewpoint, as a result of research to improve the adhesion of the hard particles in the Fe-based sintered alloy forming the valve seat to the base material, the hard particles were determined to be Co-based alloy, preferably, in weight% (hereinafter ,% Indicates weight%), Cr: 15 to 30%, Mo: 5 to 20
%, Ni: 5 to 20%, Fe: 5 to 20%,
C: 0.5 to 3%, the rest is specified as a Co-based alloy having a composition of Co and inevitable impurities, and the base is an Fe-based alloy, preferably C: 0.5 to 2%.
Ni: 3-10%, Co: 0.5-8%,
Mo: 0.5 to 2% is contained, and the rest is specified as an Fe-based alloy having a composition of Fe and inevitable impurities, and the ratio of the hard particles is preferably 5 in the total.
When the alloy layer containing Ni as the main component is interposed at the interface between the hard particles of the Co-based alloy and the base material of the Fe-based alloy, the hard particles and the base material of the alloy layer are limited to 25% to 25%. Since the bonding force to both of the above is extremely high, the adhesion of the hard particles to the base material is significantly improved, and the resulting Fe-based sintered alloy valve seat is practically used under severe conditions. Since the peeling of the hard particles from the substrate is remarkably suppressed, the research results that excellent wear resistance is exhibited for a long period of time were obtained.

The present invention was made based on the above-mentioned research results, and is an Fe-based alloy, preferably C:
0.5-2%, Ni: 3-10%, Co:
0.5 to 8%, Mo: 0.5 to 2%, and the balance of Fe and unavoidable impurities in the base of the Fe-based alloy, Co-based alloy, preferably Cr: 15-3
0%, Mo: 5-20%, Ni: 5-20%,
Fe having a structure in which hard particles of a Co-based alloy containing Fe: 5 to 20% and C: 0.5 to 3% and the balance of Fe and unavoidable impurities are dispersedly distributed.
In a method for manufacturing a valve seat composed of a base sintered alloy, an alloy layer containing Ni as a main component is continuously and / or intermittently present at an interface between the hard particles and a base material to form the hard particles. It is characterized by a method for improving the wear resistance of a valve seat made of a Fe-based sintered alloy by improving the adhesion to the base material.

[0006]

Next, the method of the present invention will be specifically described with reference to examples. As a raw material powder for forming hard particles, each has a predetermined average particle size within the range of 47 to 69 μm and Table 1
Co-based alloy powders A to K having the composition shown in Table 1 are prepared, and 100 as a raw material powder for forming a base material.
A Ni powder, a Co powder, a Mo powder, an Fe powder, and a graphite powder each having a particle size of less than or equal to μm are prepared. After mixing together with the quantitative amount, this was heated in a hydrogen atmosphere at 900 ° C. for 1 hour, cooled, and then crushed to obtain a Ni-coated Co-based alloy powder. Blend to the formulation shown below, add 1% zinc stearate as a lubricant and mix for 30 minutes in a mixer, then add 7 ton / cm ²
Press forming into a green compact with the pressure of
For 30 minutes to degrease, then in vacuum, 1100-
Inventive methods 1 to 13 and conventional methods 1 to 1 by sintering at a predetermined temperature in the range of 1200 ° C. for 1 hour.
3 each, and in each case, outer diameter: 34 mm x thickness: 7
An Fe-based sintered alloy valve seat having a size of mm and a composition substantially the same as the above-described composition was produced.

The various valve seats obtained as a result were subjected to a wear test for the purpose of evaluating wear resistance.
For the wear test, the valve seat was installed in a gasoline engine with a displacement of 2000cc, unleaded gasoline was used, valve material: JIS / SUH35, engine speed: 600
The maximum wear depth of the valve seat and the maximum wear depth of the valve, which is a mating member, were measured under the conditions of 0 rpm and test time: 100 hours. The results of these measurements are shown in Table 4.

[0008]

[Table 1]

[0009]

[Table 2]

[0010]

[Table 3]

[0011]

[Table 4]

[0012]

From the results shown in Table 4, the method of the present invention 1 to
The valve seat made of the Fe-based sintered alloy manufactured by No. 13 is an alloy layer containing Ni as a main component existing at the interface between the hard particles of the Fe-based sintered alloy and the base material that compose the valve seat (the raw material powder during sintering. Ni-coated Co-based alloy powder coated Ni
Inside, the Co-based alloy constituting the hard particles and the constituent components of the base material form a solid solution to form an alloy layer containing Ni as a main component) so that the adhesion of the hard particles to the base material is significantly improved. Therefore, even under the above-mentioned high-speed operating conditions, while exhibiting excellent wear resistance in a state of low opponent attack, the Fe-based sintered alloy valve seat manufactured by the conventional methods 1 to 13 has It is clear that since the hard particles do not have sufficient adhesion to the substrate, the hard particles are liable to peel off, resulting in inferior properties in both wear resistance and opponent attack. As described above, according to the method of the present invention, it is possible to manufacture a valve seat composed of an Fe-based sintered alloy having excellent adhesion of the hard particles to the green body, and thus the resulting Fe-based sintered bond is produced. Gold valve seats have a low opponent attack even under harsh conditions and exhibit excellent wear resistance.

Front Page Continuation (72) Inventor Toru Kono 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Central Research Laboratory, Mitsubishi Materiality Co., Ltd.

Claims (1)

[Claims] 1. A method for manufacturing a valve seat comprising a Fe-based sintered alloy having a structure in which hard particles of a Co-based alloy are dispersed and distributed on a base of an Fe-based alloy, wherein an interface portion between the hard particles and the matrix is used. Made of an Fe-based sintered alloy having excellent wear resistance, characterized in that an alloy layer containing Ni as a main component is continuously and / or intermittently present to improve the adhesion of the hard particles to the base material. Valve seat manufacturing method.